Single-chamber clearance unloader



1,625,681 APrll 19,1927 w. PRELLWITZ SINGLE CHAMBER CLEARANCE UNLOADER Filed July 27. 1926 2 Sheets-Sheet 1 INVENTOR. 11 1M mfl ellw'itj HIS ATTC' EY.

1,625,681 April 1927' w. PRELLWH'Z SINGLE CHAMBER CLEARANCE UNLOADER Fi led July 27. 1926 2 Sheets-Sheet 2 H15 ATT RNEY Patented Apr. 19, 1927.

master UNlTED STATES PATENT OFFICE.

WILLIAM PRELLWITZ, OF EASTON, PENNSYLVANIA, ASSIGNOR TO INGERSOLL-RAND COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPGRATION OF NEW' JERSEY.

SINGLE-CHAMBER CLEARANCE UNLOADER.

This invention relates to compressors, but more particularly to a clearance unloader having a single clearance chamber.

The objects of the invention are to enable a single clearance chamber to be used for either end of the cylinder in a step by step unloading system so that the same chamber may be conveniently used twice in the series of steps, the remaining steps or parts 01" steps being effected by unloading devices of some other type, such as inlet valve unloaders for instance.

The single clearance chamber may be provided with two clearance valves, alternately opened and closed, so that the same chamher is first thrown solely into communication with one end of the cylinder and then solely into communication with the other end of the cylinder, thus reducing the clearance space required in a compressor, and leaving more needed room for inlet and discharge valves.

The invention is shown in one suitable form in the accompanying drawing, in which Figure l is a diagrammatic representation of an unloading system partly in longitudinal sectional elevation, and

Figures 2, 8, i and 5 are diagrammatic views in section showing difi'erent positions of unloading.

Referring to the drawings, the cylinder A is provided with a piston B, and the air drawn from the intake 0 is discharged through the discharge pipe D to the receiver E in the usual manner.

The cylinder is provided With the inlet valves F and G, which may be plate valves of any suitable type, each provided with valve openers H and J of any suitable form, having fingers K and L and the pistons O and P in the cylinders Q and B. These cylinders are preferably provided with the leak ports S and T to permit the pistons O and P to be quickly retracted by the springs U and V. The valves F and are held open by receiver pressure supplied through the pipes 2 and a respectively, and connected to a single regulator Y, to be described. The discharge valves Z for the cylinder only .indicated diagrammatically may be of any suitable type as for instance, plate valves and there may be a plurality .of both inlet and discharge valves foreach end of the cylinder. v v

,The' cylinder is provided with a'single clearance chamber and in this instance the clearance chamber "V may conveniently be formed in the end head a and connected by the passage X with the opposite end of the cylinder. It is to be understood, however, that the chamber V? and passage X together form a single clearance chamber and the relative volumes of the chamber TV and passage X may be varied as desired. Preferably the volumes are about equal and the total clearance space is designed to half unload one end of the cylinder at a time.

In accordance with this invention the single clearance chamber WV, X is provided with two clearance valves Z) and b one for each end of the cylinder. Each valve is provided with a piston 0 operating in a cylinder (Z and normally pressed to its seat 6 by the spring 7". The cylinder A is preferably provided with the leak port 9 and another leak port it leads from the forward end of the cylinder in front of the piston 0. Each clearance valve is adapted to be opened and held opened by receiver pressure supplied through the pipes 1 and 3 connected to the regulator Y. The pipe is connects the receiver E with the regulator, as shown.

The regulator Y in this instance comprises a cylinder having a piston 0 which forms a valve and controls the ports p, r, s, t and u in the wall of the regulator cylinder. The pipe 2 leading to the inlet valve plunger Q has three branches leading to the ports 1' and t. The piston valve 0 is actuated in one direction by a receiver pressure and in the opposite direction by the spring 4) having the adjusting screw 10. A leak port a: is provided for that end of the regulator in which the spring is located. The piston valve 0 is conveniently provided with'the passage 1 communicating with the port 2. This piston valve 0 is also provided with the passage 5 communicating with the port 6 in a different angular plain on the surface of the piston valve from the plain in which the port a is located so that during the longitudinal move ill) ment of the piston 0 the ports in the cylinder wall, lettered from p to a respectively, are controlled in a certain order by the ports a and .6. g

In the operation of the device, let it be assumed that the clearance valves 6 and b are closed as indicated in the drawing, and that'theinlet valve openers are retracted, so that the inlet valves are functioning normally. In such case the compressor will be under full load and the regulator is so constructed that the compressor in unloaded step by step, in accordance with the discharge pressure, that is, three-quarter load, one-half load, one-quarter load, and no load, permitting five steps of control from full load to no load, although the number of steps may be varied as desired.

In accordance with this invention, as the piston valve 0 moves longitudinally in its cylinder, the clearance valve 1) is first opened thus throwing the clea 'ance chamber \V, X into comnmnicatio i solely with one end of the cylinder which unloads the cylinder onequarter and produces tln'ee'quarters load. In the next step the cleaance alve b is closed and the inlet *alve F is opened to produce one-hall load at the same end of the cylinder. In tlie third step, the clearance valve 2) remains closed, the inlet valve F continues to remain open, and the clearance valve b is opened which throws the clearance chamber W, X into communication solely with the opposite end of the cylinder but isnever in communication with both ends of the cylinder at the same time and unloads the cylinder three-quarters producing one-quarter load. In the final step the clearance valve 1) is preferably closed, the inlet valve F at one end of the cylinder remains open and the inlet valve Gr at the opposite end of the cylinder is opened to produce a condition of no load. In this cycle of operations it will be observed that the single clearance chamber IV, X functions alternately for both ends of the cylinder and as the cycleof operations is repeated in the reverse order for loading the compressor, the clearance valves 6 and Z) both function alternately.

In carrying out the series of steps, as the piston valve 0 moves from the position indicated in the figure to the right, the port .2 first comes opposite the port 7) which per inits receiver pressure to pass through pipe 1 and withdraws the piston 0 thus opening the clearance valve 1) at one end of the cylinder, and producing the condition of three-quarters load. The port a in the piston valve passes by the port a and next re isters with the port 9, at the same time c osing port 79 so that receiver pressure is cut oil from the piston of the clearance valve Z) and this valve closes due to leakage through the leak port it. Receiver pressure, however, passes through the pipe 2 to the piston 0 of the inlet valve opener of the valve F holding this valve open and producing onehalf load on the compressor. The port .2 next registerswith the port 1* which is in communication with the pipe 2* so that the inlet valve F continues to be held open While at the same time the port 6 in the piston valve o registers with the port 8 permitting receiver pressure to pass through the pipe 3 and open the clearance valve 7/ at the opposite end oi the cylinder, thus producing the condition of one-quarter load since the opposite end of the cylinder is fully unloaded. The alternate operation of the clearance valves Z2 and b has taken place. In the net-1t and linal step the port 2 registers with the port t thereby continuing to maintain the inlet valve F open and the port 8 is closed which permits the clearance valve 7) to close. and the port (3 registers with the port a thus: permitting receiver pressure to pass through the pipe 4- and open the inlet valve at the opposite cud oi the cylinder from the inlet valve F, 1-o that the cylindcr is completely unlomled. As the piston valve 0 H'IOVGS rcarwardly in reversed direction the cycle oi operations is repeated in reverse order for loading the compressor. Means may be provided if desired, to prevent the piston valve 0 from rotating in the regulator cylinder about its own axis and torthis purpose a key or leather 7 may he provided for guiding the piston valve and l'n'cventing it from rotating.

Figures 2, 3, a and 5 are diagrammatic sectional views which aid in an understanding of the invention, since they show the relative positions oi the regulating valve, clearance valves and inlet valves din-inc the various steps of unloading, from threequarters load to no load inclusive.

Obviously the last step of unloading could be effected by again opening the clearance alve 7) instead of opening the inlet valve G. If both clearance valves were open, the compressor would be fully unloaded since air would pass freely from one end to the other through the bypass afforded by theclearance chamber IV, X.

I claim:

1. In a compressor unloader, the combination of a cylinder and piston, a single clearance chamber, and means for alternately placing said chamber solely in communication with either one end or the other of the cylinder for unloading purposes.

2. In a. compressor, the combination oi a cylinder and piston, inlet and discharge valves, a single clearance chamber, and a plurality of clearance valves for said chamber, one for each end of the cylinder, whereby said chamber may be alternately placed in communication solely with either one end or the otherof the cylinder for unloading purposes.

3. Ina compressor, the combination ot a cylinder and piston, inlet and discharge valves, a single clearance chamber, a plurality of clearance valves for said chamber, one for each end of the cylinder, and means for alternately opening one clearance valve and closing the other of said clearance valves, whereby said chamber may he altertill llill nately placed in communication solely with either one end or the other of the cylinder for unloading purposes.

4. In a compressor, the combination of a cylinder and piston, inlet and discharge valves, a single clearance chamber, a plurality of clearance valves for said chamber, one for each end of the cylinder, and means for unloading the compressor in steps by first opening the clearance valve for one end of the cylinder, then holding an inlet valve open at the same end of the cylinder, then closing the first said clearance valve and opening the clearance valve for the opposite end of the cylinder while maintaining said inlet valve open, and finally opening the inlet valve at the opposite end of the cylinder from said first named inlet valve, while continuing to hold said first named v inlet valve open.

5. In a compressor, the combination of a cylinder and piston, inlet and discharge valves, a single clearance chamber, a plurality of clearance valves for said chamber, one for each end of the cylinder, and means for unloading the compressor in steps by first opening the clearance valve for one end of the cylinder, then holding an inlet valve open at the same end of the cylinder, then closing the first said clearance valve and opening the clearance valve for the opposite end of the cylinder while maintaining said inlet valve open, and finally closing said last named clearance valve and opening the inlet valve at the opposite end of the cylinder from said first named inlet valve, while continuing to hold said first named inlet valve open.

6. In a compressor unloader, the combination of a cylinder and piston, inlet and discharge valves, a single clearance chamber, and means for automatically placing said chamber first in communication solely with one end of the cylinder and then solely in communication with the other end to effect steps of unloading.

7. In a compressor unloader, the combination of a cylinder and piston, inlet and discharge valves, a single clearance chamber, means for automatically placing said chamber first in communication solely with one end of the cylinder and then solely in communication with the other end to effect steps of unloading, and means for efiecting alternate steps of unloading by holding open inlet valves.

8. In a step by step unloading system tor compressors, the combination of a cylinder and piston, a single clearance chamber. means for effecting one complete step of unloading at one end of the cylinder by utilization of the said chamber in communica tion solely with said end of the cylinder, and means for efiecting a partial step of unloading by utilization of the same chamber but solely in communication with the opposite end of the cylinder.

In testimony whereof I have signed this specification.

WILLIAM PRELLWITZ. 

